Comparison of standard, prone and cine MRI in the evaluation of tethered cord

Abstract

Conus level provides the highest diagnostic accuracy and inter-reader reliability in TCS. Until a larger series is evaluated, it remains questionable whether prone or cine MRI provides enough additional diagnostic information to warrant routine use.

Magnetic resonance imaging in the prone position and the diagnosis of tethered spinal cord

“…Previously reported sensitivities and specificities for prone MRI in diagnosing tethered cord range from 62% to 67%, slightly lower than the sensitivity of looking at the conus tip level (69%-77%). 18 In our sample, there was no threshold in degree of ventral conus motion, in terms of absolute distance or percentage of canal width, which perfectly separated the normal controls from the surgically documented tethered and retethered groups. Whereas all 30 of our patients in the normal control group exhibited > 10% motion, there were 3 patients in our tethered or retethered groups with > 10% motion (2/41 with 10%-15% motion, 1/41 with 16% motion).…”

“…1,[3][4][5]8,11 Cord motion on MRI has been measured by both the phase-contrast cine technique and by obtaining prone sequences. 18 The normal spinal cord moves craniocaudally at approximately 1 cm/second in opposition with CSF during systole and diastole, and dampening of this velocity by using phase-contrast MRI has been demonstrated in patients with tethered cord. 2,11 This technique, however, requires careful calibration of the MR scanner to make accurate velocity measurements, and the current lack of a large series demonstrating its accuracy has further limited its use at most institutions.…”

“…12 Magnetic resonance sequences with prone imaging, first described in 1996 by Vernet et al, 21 can show ventral conus movement related to gravity in patients with normal spinal cords 22 and can imply laxity of the spinal cord; however, results have been mixed in the available literature when assessing cord motion in patients with cord tethering and retethering. 13,18,21 Despite the limitations of MRI, it remains preferred as a noninvasive technique for the evaluation of spinal pathology and in supporting the diagnosis of TCS.…”

The Use of Prone Magnetic Resonance Imaging to Rule Out Tethered Cord in Patients With Structural Spine Anomalies: A Diagnostic Technical Note for Surgical Decision-making

“…Assessing conus terminalis anterior movement can be a useful way to rule out spinal cord tethering in adult patients showing anatomical features of structural cord malformation, such as spina bifida, split cord malformation, and a fatty filum terminale. The usefulness of obtaining a prone MRI has been previously described, but mostly in pediatric patients series, and in a retrospective fashion after surgery had already been performed [3-4,10-11]. Although this report is based on a single case, it showcases the practical advantage of obtaining prone MRI imaging in adult patients presenting with atypical spinal complaints such as back pain with ambulation and intermittent radicular symptoms, especially if they have an associated anatomical spinal cord anomaly.…”

“…While surgery can provide significant symptomatic improvement in the right patient, complications are not benign and range from spinal fluid leakage and meningitis, to wound dehiscence requiring expansile flap grafting, with a chance of persistence or early recurrence of the presenting neurological symptoms [8-9]. There have been reports of using prone MRI to assess the anteroposterior movement of the conus in the setting of TCS, but most studies have involved pediatric populations, or have been retrospective and purely descriptive in nature, and provided equivocal results [3-4]. We present a case where comparative imaging between prone and supine MRI was used to successfully steer the decision towards the non-surgical management of a patient with split cord malformation and low-lying conus, who presented with equivocal symptoms.…”